Improvement of the mechanical, tribological properties and oxidation resistance of AlCrVN coatings by Nb alloying

In this study, the effect of Nb alloying on AlCrVN coatings was systematically investigated, with emphasis on their microstructure, mechanical and tribological properties and oxidation resistance. With the alloying of Nb, the phase composition of these coatings changed from c-AlCrVN soild solution, c-VN and a small amount of h-AlCrN to c-AlCrNbN soild solution and a small amount of h-NbCr2. The alloying of Nb transfered the preferred orientation from (111) to (200), and the intensity increased with an increase in Nb. The microstructure of the coatings transformed from short and coarse columnar to coarse columnar, and then to compact slender columnar. Although the vary in V and Nb content had little influence on the hardness, it had a comparatively influence on the elastic modulus. The synergistic effect of Nb and V was as follows: (1) the highest ratios of H/E (∼0.100) and H3/E2 (∼0.318) were obtained for Al0.6Cr0.28V0.08Nb0.04N, and the highest adhesion (∼79.5 ± 3.5 N) for Al0.59Cr0.28V0.04Nb0.09N; (2) the lowest coefficient of friction of ∼0.392 (Al0.6Cr0.28V0.08Nb0.04N) and the lowest wear rate of 1.42 × 10−7 mm3/(N·m) (Al0.59Cr0.28V0.04Nb0.09N); (3) the onset temperature of oxide from 800 °C (Al0.6Cr0.28V0.12N) to 1000 °C (Al0.59Cr0.28V0.04Nb0.09N).